1) Technical Field of the Invention
The present invention relates to a resin-molded device having a resin package holding together a plurality of electronic elements, lead frames (lead members), and metal blocks for radiating heat, and also relates to a manufacturing apparatus of the resin-molded device.
2) Description of Related Arts
An example of the resin-molded electronic devices is a power semiconductor device commonly used as a switching inverter device incorporated in an electronic appliance such as an air conditioner and a washing machine. As illustrated in FIG. 22, the power semiconductor device includes, in general, a plurality of lead frames 101, a power element 102, a metal block 103 serving as a heat sink for radiating heat. The power semiconductor device also includes a resin package 104 holding together those above-mentioned components.
The lead frame 101 includes a die pad portion 105 and an inner lead portion 106. The power element 102 is bonded to the upper surface of the die pad portion 106 via solder 107. Also, the power element 102 is electrically connected to the inner lead portion 106 via an aluminum wire 108. A metal block 103 has a plateau portion 109 formed substantially in the middle region of the metal block 102. The plateau portion 109 is arranged beneath the lower surface of the lead frame 101 so as to oppose to power element 102 and spaced from the lower surface of the lead frame 101 with a predetermined gap. A portion of the resin package 104 sandwiched between the plateau portion 109 of the metal block 103 and the lead frame 101 is referred to as a insulating resin layer 110. The power element 102, the lead frames 101, and the metal block 103 are together held in the resin package 104, while the bottom surface of the metal block 103 opposing to the top surface adjacent to the lead frame 101 is uncovered or exposed. Although not shown, an external radiator is secured on the exposed bottom surface of the metal block 103.
In such a conventional power semiconductor device, heat generated by the power element 102 is radiated through the lead frame 101, the insulating resin layer 110, and the metal block 103 to the external radiator. The metal block 103 is made of metal such as aluminum and copper having thermal conductivity of 200 W/mxc2x7K and 390 W/mxc2x7K, respectively. Since the lead frame 101 is made of metal such as copper, it has thermal conductivity similar to one of the metal block 103. Meanwhile, the insulating resin layer 110 has thermal conductivity of 1-3 W/mxc2x7K, which is approximately one-hundredth ({fraction (1/100)}) of those of the lead frame 101 and the metal block 103. Therefore, the insulating resin layer 110 has a main controlling factor to the heat conductivity of the power semiconductor device. In other words, an internal heat resistance of the conventional power semiconductor device depends mostly upon the insulating resin layer 110.
The heat resistance or heat radiating performance of a material is determined, in general, based upon a heat radiating thickness, a heat radiating area, and thermal conductivity of the material. Thus, the internal heat resistance of the power semiconductor device may be reduced by thinning the insulating resin layer 110. However, since the dielectric breakdown voltage of the insulating resin layer 110 is required more than several thousands volts, it is known that it can not be thinner than approximately 0.3 mm. This limits improvement of the heat resistance by thinning the insulating resin layer 110.
Thus, in order to further improve the heat radiating performance of the power semiconductor device, the metal block serving as a heat spreader has been proposed, which has a wider surface extending towards the upper stream, thereby increasing the heat radiating surface. In the power semiconductor device including a plurality of power elements, it should also includes a plurality of the metal blocks, which have to be electrically isolated from one another for the necessity of electrical isolation of the power elements from each other. Nonetheless, in a molding step of the resin package of the conventional power semiconductor device including several metal blocks, no special care has been taken to fill up the channels defined between the adjacent metal blocks with resin in a reliable manner. Thus, the conventional power semiconductor device including several metal blocks has several problems to be addressed as described hereinafter.
Referring to FIGS. 23 to 26, the above-mentioned problems will be described herein in detail. FIG. 23 is a top plan view of the conventional semiconductor device before molding the resin package 104. As described in JPA 2000-138343, fluid resin is injected from a plurality of resin runners 111 of a molding die through the corresponding resin inlet of the semiconductor device so as to form the resin package 104. FIG. 24 is a bottom plane view of the conventional semiconductor device schematically illustrating the plurality of the metal blocks 103 and the resin runners 111 while fluid resin is being injected from the resin runners 111 during the resin package molding step. A plurality of channels 112a to 112c are defined between the metal blocks 103 adjacent to each other, and the fluid resin reach into them at a different timing, as shown in FIG. 24. Thus, the front-running resin reached in the channels 112b, 112c pushes the metal blocks 103 towards the channel 112a of the behind-running resin due to the resin injection pressure. The first problem of the conventional semiconductor device is that the metal blocks 103 are shifted so that the channels 112b, 112c of the front-running resin are expanded and the channel 112a of the behind-running resin is pinched.
As above, the fluid resin is filled in the channel 112a some time after filled in the channels 112b, 112c. Thus, the channels 112b, 112c become wider and the channel 112a is narrower than that before the molding step. Since the fluid resin is less likely to reach the narrower channel 112a, completion to fill in the narrower channel 112a is more delayed in comparison with the other channels 112b, 112c. Eventually, the adjacent metal blocks 103 sandwiching the narrower channel 112a may contact with each other so that the electric isolation (insulation) therebetween can not be secured, thereby resulting in the fatal defect of the semiconductor device. Also, in case where the adjacent metal blocks 103 sandwiching the narrower channel 112a have the substantial amount of stress applied thereto, the bonding layers between the lead frames and the metal blocks may have a critical damage.
Secondly, even where contact between the metal blocks are avoided, the fluid resin is less likely injected in the narrower channel 112a so that the resin-unfilled hollow portions are defined therein. This may also cause insufficiency of electrical isolation between the adjacent metal blocks, resulting in the fatal defect of the semiconductor device.
Thirdly, even where shift of the metal blocks is prevented, if air is trapped between the metal blocks and not evacuated, the remaining air forms so-called a xe2x80x9cvoidxe2x80x9d so that electrical isolation cannot be secured between the metal blocks. Thus, the usage of the conventional resin runners cause the resin injection timing for each of the channels different from one another, thus, the fluid resin turns around, thereby remaining air between the metal blocks, which is referred to as the void.
Also, FIG. 25 is a schematic bottom view of the conventional semiconductor device similar to FIG. 24, but after the channels are completely filled up with the fluid resin. In this drawing, the running directions of the fluid resin are illustrated by the arrows. As above, the fluid resin is delayed to reach the channel 112a, the channel 112a is filled up not only with the fluid resin directly from the resin runners 111 but also with fluid resin turning around from other channels 112b, 112c. Those fluid resin trap air, thereby forming the void 114 in the channel 112a, which in turn, reduces the isolation performance between the adjacent metal blocks 103.
There is the fourth problem especially in so-called a full-molded semiconductor device, in which the metal blocks are entirely encompassed by the resin package. In such a full-molded semiconductor device, the resin package fully covers the bottom surface of the metal block adjacent to the external radiator so that electric isolation between the metal block and the external radiator can be secured. Nonetheless, also because of the turning-around of the fluid resin, the resin-unfilled portion or void 115 can be formed on an insulating layer adjacent to the bottom surface of the metal blocks as shown in FIG. 26. that is a schematic bottom view of the conventional full-molded semiconductor device similar to FIGS. 24, 25. Because the resin-unfilled portion or void 115 is formed exposing the metal block 103, electric isolation between the metal block and the external radiator cannot be secured, thereby resulting in the product failure.
Therefore, the aspects of the present invention has a purpose to address those problems as described above, and to provide a resin-molded device with a resin package having an improved insulation performance, and a manufacturing apparatus thereof.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the sprit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The first aspect of the present invention is to provide a resin-molded device including a plurality of electronic elements spaced from each other. It also has a plurality of lead members, each one of the lead members electrically connecting to the corresponding one of the electronic elements. Further, it has a plurality of metal blocks spaced from each other so that a plurality of channel portions are defined between the metal blocks. Each of the metal blocks is arranged so as to correspond to at least one of the electronic elements and the lead members connected to the electronic element. The resin-molded device includes a resin package of electrically insulating material molded so as to hold together the plurality of the electronic elements, the lead members, and the metal blocks. The resin package includes a plurality of resin inlets through which fluid resin is injected, and wherein each of the resin inlets opposes to the corresponding one of the channel portions.
The second aspect of the present invention is to provide a manufacturing apparatus of a resin-molded device, which include a plurality of electronic elements spaced from each other, a plurality of lead members, each one of the lead members electrically connecting to the corresponding one of the electronic elements. In the device, a plurality of metal blocks are spaced from each other so that a plurality of channel portions are defined between the metal blocks. Each of the metal blocks is arranged so as to correspond to at least one of the electronic elements and the lead members connected to the electronic element. The resin-molded device also includes a resin package of electrically insulating material molded so as to hold together the plurality of the electronic elements, the lead members, and the metal blocks. The manufacturing apparatus includes a molding die for molding the resin package. The molding die includes a plurality of runner portions from which fluid resin is injected, and each of the runner portions opposes to the corresponding one of the channel portions.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the sprit and scope of the invention will become apparent to those skilled in the art from this detailed description.